This invention relates to an improvement in a data processing terminal unit containing a cassette type magnetic tape therein.
In the past, there have been developed data transaction or manipulation systems of the type wherein data entries occurring at a point of sale terminal such as utilized in a retail sales store are recorded through a keyboard on a cassette type magnetic tape which in turn, is coupled with a central data processing computer system through a medium converter such as a tape to tape converter. When it is desired to record data entries on the cassette tape, predetermined markings such as a tape mark (TM) and an end mark (EM) should be written at the beginning point and ending point of data record field of the cassette tape. In the event that the operator erroneously instructs to enter EM signals into the cassette tape at an undesired time, this will result in erroneous operation when handling data received form the data processing terminal unit, since the central data processing computer system is adapted to handle only the data interposed between the TM mark and the EM mark.
Accordingly, it is an object of the present invention to provide a data processing terminal unit which can prevent erroneous introduction of the EM signals into the data processing terminal unit at an undesired time.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter; it should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention wlll become apparent to those skilled in the art from this detailed description.
To achieve the above objective, the data processing terminal unit of the present invention is provided with a first entry key or an E key and a second entry key or an M key on a keyboard thereof. The EM signals are introduced into the data processing terminal unit when the E key and the M key are depressed in succession or simultaneously.